1. Field of the Invention
The present invention relates to pointing devices for computers, and in particular, to pointing devices having a sliding panel.
2. Description of Related Art
The popular, graphical, user interfaces require a pointing device. The two most commonly used devices are the mouse and the track ball. The mouse can be connected by a cable to a serial port of a computer. The mouse is normally operated on a nearby desktop pad. A mouse is generally inconvenient for use with a portable computer, since such computers attempt to minimize space requirements and may often be operated on the user's lap because a desktop is unavailable. See U.S. Pat. Nos. 5,298,919 and 5,311,208.
A commonly used pointing device for a portable computer is a track ball mounted in the keyboard. The track ball is a sphere mounted to rotate with three degrees of freedom, although only two degrees are measured since the cursor being controlled can only move two dimensionally. A disadvantage with the track ball is the somewhat unnatural need to repetitively stroke the ball to move the cursor across the screen. Also, the track ball lacks the intuitively natural facility of depressing a pushbutton with the index finger at the destination without repositioning the fingers. Instead, track balls normally have a pushbutton spaced from the ball. U.S. Pat. No. 5,309,172 shows a track ball mounted in a computer keyboard. See also U.S. Pat. Nos. 5,341,154 and U.S. Pat. No. 5,386,089.
Another popular type of pointing device is a deflectable knob located between keys on the keyboard of a portable computer. The pointer is moved on the screen in a direction and speed dependent upon the direction and strength with which the deflectable knob is pushed.
U.S. Pat. No. 4,670,743 shows a pointing device in the form of a knob (no "clicking" pushbutton) that can slide in two directions at the top deck of an oversized computer keyboard. The knob is mounted on dual slides that carry dual encoder strips and thus lacks a two dimensionally moveable panel. The arrival of the slider knob to an extreme edge position is sensed and temporarily freezes the cursor while the knob is retracted from the edge. Cursor motion is restored when the knob reverses direction. Still, this reference lacks the ability found in a mouse to be lifted and repositioned while the cursor remains stationary.
U.S. Pat. No. 5,400,054 shows in FIGS. 1-3, a pointing device in the form of a separate accessory with a plate that can slide two dimensionally. The plate is moved by a handle having a pushbutton. Motion of the plate is detected by one or more roller balls. Another function button on the handle can be used to disable the pointing device when retracted, thereby achieving the function performed by lifting and repositioning of a conventional mouse. Keyboard mounting is mentioned at column 7, lines 63-65, apparently referring to an embodiment where the sliding plate is replaced with a fabric stretched around a donut-shaped holder.
See also U.S. Pat. Nos. 4,459,575; 4,795,862; 4,831,736; 4,879,556; 5,245,320; and 5,407,285.
U.S. Pat. Nos. 3,643,148; 4,670,743; 4,748,441; and 5,488,392 were cited in the parent application.
Accordingly, there is a need for a pointing device that can be readily adapted to various computers, including adapting to keyboard mounting in portable computers; while retaining the intuitively natural features of some pointing devices, such a mouse.